Can ipv4 and ipv6 co-exist?
Not only can they coexist, but they actually need to! The transition from IPv4 to IPv6 will take several years, during which time both protocols need to be used. Whilst there are still a few issues in isolated cases of IPv4/IPv6 co-existence, software and hardware vendors are working hard to resolve them and there should be no serious reason for both protocols not to co-exist for years to come.
